Refined metal, which is usually in molten form after an initial separation process, is cast into ingots or billets as an intermediate operation between the smelting and further treatment of the metal. In the aluminum industry, the metal is normally formed into billets which are generally cylindrical in shape, and sawed to desired lengths depending upon the requirements of further processing steps, such as extruding or rolling. Cylindrical aluminum billets typically have diameters ranging from 6 inches up to 20 inches. The nominal length of aluminum billets also varies widely, normally between 16 inches to 36 inches. In many cases the billets which have been produced by a particular metal processing plant are shipped to a different location for further processing. In order to ship and handle the billets they must be lifted, preferably in groups or rows, to facilitate storage and stacking procedures.
In the aluminum industry numerous billets are cast and cut at one time and it is desirable to have a billet grab which can lift and move a number of billets at one time. Due to the way they are formed to length, normally by cutting, the billets might have identical or slightly varying lengths. Since the cut billets are usually arranged side by side in a row, it is desirable to have a billet grab which can automatically adjust for differing individual billet lengths in each row.
One example of a billet lifting device is U.S. Pat. No. 2,647,007 to C. H. Gmoser. The Gmoser patent discloses an adjustable lifting clamp for lifting a single metal ingot or billet. The lifting clamp must be manually positioned with the ends of the clamp on opposite sides of the billet. One end of the clamp is then manually adjusted until both sides of the clamp are engaged with opposite sides of the billet. One end of the clamp has a pivotally mounted cam which, through direct mechanical linkage with the lifting shackle on the clamp is pivoted and forced into the end of the billet. As the billet is lifted, the lifting action on the shackle of the lifting clamp forces the cam further into the side of the billet until the billet is firmly held between the jaws of the lifting clamp. The Gmoser clamp is suitable only to lift a single billet, and is not adaptable to lift a number of billets at one time. In addition, the Gmoser clamp must be manually positioned over the billet to be lifted and the movable jaw must be manually positioned so that both jaws of the lifting clamp are in engagement with the billet. The cammed billet engaging surface on one jaw is mechanically driven through a direct mechanical connection with the lifting clamp.
Another prior art billet grab is shown in U.S. Pat. No. 4,261,609 to Kraszewski. The Kraszewski patent discloses an ingot grab apparatus having a pair of grab legs supported for horizontal movement toward and away from one another. Each of the grab legs has a grip point mounted on the leg for movement along an incline which extends downwardly and inwardly and upwardly and outwardly. The grip points on each grab leg face one another for engagement with side surfaces or opposite ends of an ingot. When the legs are moved toward one another, the points engage opposite sides or ends of the ingot. As the carrier is elevated and the grip points bear the weight of the ingot, the grip points are forced downwardly and inwardly into the ingot for secure lifting engagement. The lift points in the Kraszewski ingot grab are biased into their upward position by a spring when an ingot is not engaged between the legs. Once the grip points are engaged and are carrying the weight of the ingot, a spring-loaded locking device moves outwardly and prevents any upward movement of the grab points when the ingot is lifted. The Kraszewski ingot grab is suitable only for lifting one ingot at a time, since the grab points are biased upwardly when they are not engaged, and a shorter ingot in a row of ingots would not be engaged by the grip point, and therefore would not be lifted by the ingot grab.